Bottom Status Bar Doesn't Show Verts, Faces, Tris Information In v2.9a
As of Blender 2.9+ scene statistics are now part of the 3D view and integrated into each viewport.
That is where they always belonged, since each specific view could have different visibility and selection states, resulting in different statistics. This now allows showing more relevant information for each independent viewport, reflecting individual variations.
They can be activated from the Overlays Popover in the 3D View Header.

To mitigate the lack of an unobtrusive way to display global scene statistics without a permanent overlay over the 3D View, and still be able to show system stats like available memory, customizable statistics to the status bar was reintroduced in 2.90.1.